The invention relates to a brake device for an automobile and, more particularly, a vehicle-mounted brake device for generating a braking force by using an electric power.
Hitherto, a brake device for generating a braking force by making electrically driven motors operative has been known. For example, according to the brake device proposed in JP-A-11-321599, a vehicle motion controller transmits a required braking force to a drive controller in accordance with an output of a pedal sensor for detecting depression quantity of a brake pedal, an output of a thrust sensor for detecting a thrust of an actuator, and an output of a wheel speed sensor, and a frictional material is pressed onto a disk rotor by the actuator which is driven by the drive controller, thereby applying the braking force to wheels.
According to the brake device, advanced vehicle controls such as anti-lock control, automatic brake control, and the like and an adjustment of a brake feeling can be performed in correspondence to software. A parking brake can be also applied by using an actuator for vehicle control in common.
According to the conventional brake device, the vehicle motion controller and the drive controller are arranged on the vehicle body side (hereinafter, referred to as a spring-mass) of a vehicle having suspensions. The spring-mass is constructed by a body, an engine and a transmission which are mounted on the body, the interior, and the like. The actuator, thrust sensor, and wheel speed sensor are arranged on the wheel side (hereinafter, referred to as a unspring-mass) which is interlocked with a vertical displacement of the wheel or a motion of a steering when the vehicle body is fixed. The unspring-mass is constructed by a suspension, a knuckle, an axle, the wheel, and the like.
The drive controller and the actuator, the vehicle motion controller and the thrust sensor, and the vehicle motion controller and the wheel speed sensor are connected by electric wires, respectively. A relative displacement occurs between the spring-mass and the unspring-mass due to the motion of the suspension or the steering. Since the displacement is absorbed by deformation of the electric wires, the electric wires between the spring-mass and the unspring-mass require excellent flexibility. In addition to it, since a strength is also required in terms of countermeasures against a stone hit and freezing, a special electric wire called a bending cable is used as an electric wire. An expensive resin is also used as a sheath of the wire. A connector having excellent waterproof is necessary in a connecting portion of the electric wire and this becomes a cause of an increase in costs.
According to the conventional brake device, three bending cables for connecting the drive controller and the actuator, the vehicle motion controller and the thrust sensor, and the vehicle motion controller and the wheel speed sensor are wired with respect to each wheel, so that there is a waste of cost. A troublesomeness of wiring and the number of fixing parts which are used also increase, so that they also exert an influence on the costs. In the case where a DC brushless motor or an AC motor is used for the actuator, since a large alternating current is supplied between the drive controller and the actuator, there is a risk that noises are introduced into an ambient analog signal lines. Therefore, a cost for taking a countermeasure against the noises is needed and this exercises an influence on the costs.